Lead-varying mechanism



F. MULLER.

LEAD VARYING MECHANISM.

APPLICATION FILED FEB. 15; 19I8.

Patented July 27, 192() Q 2 SHEETS-SHEET l.

IIVVE/VTOR MM 25 BY I TORNEY F. MULLER.

LEAD VARYING MECHANISM.

APPLICATION FILED FEB. 15, 1918.

2 SHEETSSHEET 2 I 1 76 2/ J 2/ I j=- Q.Z L 19 ll I L E l/VI/E/VTOR 1'-By J. 7%

TT RA/EY UNITED STATES PATENT opener.

WHITNEY COMPANY, on NEW YORK, N.

JERSEY.

Y.,- A. CORPORATION .OF NEW LEAD-VARYING MECHANISM. I

Specification of Letters Patent. Patented J 1 i 27 1920 Applicationfiled February 15, 19 18. Serial No. 217,322.

' To all whom it may concern:

Be it known that I, FBLEDERICH MI'iLLEB, a citizen of the United States,residing at Hartford, in the county of Hartford and State ofConnecticut, :have invented certain new and useful Improvements inLead-Varying Mechanism, of which the following isa I specification.

The invention is applicable to lathes, milling machines and othermachines which are used for cutting screw threads, and its principalobject is to provide an improved mechanism by means of which the lead ofthe thread to be cut may be varied at will so as to be greater or lessthan the nominal lead, which the machine would out without the use ofthe said mechanism.

It is well known that a tap, thread gage or other threaded tool ordevice, which must he hardened after threading, requires a thread havinga lead which varies from the true nominal lead. This is necessary inorder to compensate for the change in dimensions which takes placeduring hardening. Usually the lead must be in excess of the nominal leadby afew thousandths of an inch per inch, as, ordinarily, shrinkage takesplace during hardening. The amount of shrinkage varies in accordancewith the charl acter of the metal and in accordance with the method oftreatment, and it is therefore necessary for accurate work topredetermine,'by test or otherwise, the amount of shrinkage which willtake place under given 5 conditionsand then. cut the threads with a leadwhich is in excess of the nominal lead by an amount equal to the amountof shrinkage. In accordance with. the invention, any" desired variationsin the lead within the limits of accuracy required for the closestprecision work can be easily and quickly secured.

A mechanism embodying the invention may be in the form of an attachmentadapt- 3 ed to be applied to a machine previously or separatelyconstructed, or it may constitute a permanent part of a thread cuttingmachlne. In the accompanying drawings I have shown two embodiments ofthe inven- 9 tion, each of them being a mechanism adapt ed to beappliedas an attachment to a previouslyor separately constructed lathe.It will be understood, however, that the invention is applicable tomachines other than i lathes, and it will furthermore be understood thatthe mechanism embodying the invention can be constructed as a permanentpart of the machine instead of as an attachment therefor. The drawings,therefore, are to be considered merely as illustrative and are not to beconstrued as defining or limitmg the scope of the invention, theaccompanying claims being relied upon for that purpose.

Uf the drawings:

Figure l is a front elevation of a lathe having applied thereto a leadvarying mechanism embodying the invention.

Fig. 2 is a front elevation, on an enlarged scale, of the lead varyingmechanism.

Fig. 3 is a transverse sectional view taken along the line 3-3 of Fig.2.

Fig. 4 is a plan View, partly in section, along the line 4-4 of Fig. 2.

Fig; 5 is a frontelevation similar to Fig. 2 but showing anotherembodiment of the invention.

Fig. 6 is a transverse SGCtiOIIELlxVlBW taken along the line 66 of Fig.5.

Referring to the drawings, Fig. 1 shows a lathe of standard constructionprovided with a bed 1, a headstock 2, a tailstock 3 and a tool carriage4 movable longitudinally along ways on the bed. A rotatable lead screw 5-is suitably connected with the carriage to move it longitudinally, andgearing 6 of any usual or preferred form is provided for driving thelead screw in timed relation with the rotation of the headstock spindle.Car

ried by the lathe centers is a blank A upon which are being cut threadshaving a lead slightly differing from the nominal lead.

In operation, the gearing 6 is adjusted for turning the lead screw 5 atthe proper rate to produce a thread of the nominal pitch upon the blank.By means of the mecha-- nism embodying the invention, which mechanismwill now be described, the movement of the lead screw is varied in sucha way as to cause the required variation in the lead of the thread.

Ordinarily. the lead screw of a. lathe is held against longitudinalmovement. When a mechanism embodying the invention is to be used,suitable provision must be made to permit longitudinal movement. Asillustrated, the lead screw extends through a "bearing bracket 7 whichordinarily serves,

movement. The machine can conveniently be modified to permitlongitudinal movement by cutting away one end of the bracket bolted orotherwise secured to the bed of the: lathe. The bracket is provided witha horizontal longitudinal aperture in which is fitted a sleeve 10. Thelead screw 5 extends through and has a bearing in the sleeve 10. Thesleeve 10 and the lead screw are held against relative longitudinalmovement, the sleeve, as shown, abutting against one of the collars 8 atone end and against a collar 11 at the other end. The sleeve 10 isthreaded near one end, as indicated at 12, and engages with a similarlythreaded portion of the bracket 9. It will be clear that this threadedengagement between the sleeve and the bracket will cause the sleeve onthe lead screw to be moved longitudinally when the sleeve is turned.

In order that the sleeve 10 may be turned, it is provided with gearteeth 13 which mesh with a rack 14 carried by a transverse slide 15mounted in the bracket 9. For moving the slide 15 there is provided ahorizontal taper bar 16 having a longitudinal groove 17 therein. A shoe18 projects downward from the slide 15 and enters the slot 17 It will beobvious that, if the taper bar be inclined and be moved longitudinally,the slide 15 will be moved inward or outward, thus causing a rotativemovement of the sleeve 10 and a correspondinglongitudinal movement ofthe lead screw 5.

The taper bar 16 is carried by a longitudinal slide 19 mounted on abracket 20, which is bolted or otherwise secured to'the bed of thelathe. The taper bar is pivotally connected with this slide 19 and canbe adjusted about its pivot to any desired inclination in eitherdirection. For securing the taper bar in adjusted position, there areprovided bolts 21, 21 extending respectively through slots in the endsof the bar. These bolts are respectively connected with slides movablein dovetail slots in the slide 19.

The slide 19 must be moved in timed relation with the rotation of thelead screw. As

illustrated in Figs. 1 to 4, the following which is connected with thelead screw 5 by wise, as indicated in Fig means of spur gears 23 and 24.A nut 25 engages the screw 22 and is connected di-, rectly with theslide 19 by screws,'or other- 3. 1 From the foregoing escription it will.be clear that when the lead screw 5 is turned, a. correspondingrotative movement is given to the screw 22, which in turn moves theslide 19 longitudinally. The taper bar 16, through its engagement withthe shoe 18, moves the slide 15 transversely, thus rotating the sleeve10 and moving the lead screw 5 longitudinally. It is therefore clearthat the lead screw 5 is given a steady longitudinal movement which isdefinitely related to the rotative movement thereof. This longitudinalmovement increases or decreases the net movement of the tool carriagethus changing the lead. The extent of the longitudinal movement of thelead screw can be varied as desired, within the limits of the mechanism.When the taper bar 16 is placed in exact parallelism with the slide 19there is no longitudinal movement of the lead screw. An inclination ofthe taper bar 16 in either direction causes a corresponding movement ofthe lead screw 5 in either direction and the extent of this movement canbe varied by changing the inclination of the taper bar.

When the mechanism is not to be used it is preferable, in addition toplacing the taper bar 16 in parallelism with the slide 19, to directlylock the sleeve 10 against rotation. For this purpose the bracket 9 isprovided with a vertical aperture adjacent the sleeve and in thisaperture there is positioned a shoe 26 adapted at its lower end toengage the sleeve. By means of a screw 27 the shoe may be forceddownward into firm engagement with the sleeve, thus looking it againstrotation.

If desired a scale, as shown at 28, can be provided for guidance insetting the taper bar 16. This scale can be arranged to indicate thesettings necessary for predetermined increases and decreases in theresulting pitch.

The mechanism shown in Figs. 5 and 6 is similar to that shown in Fi s. 1to 4 exce t that the slide 19 is different y actuated. n this case thesupplemental screw is omitted and the slide 19 has connected with it a.

lead screw '5, the results are the same asalready described inconnection with Figs. 1 to 4, except that the rate of movement of thesllde 19 is considerably greater. This change in the rate of movementcan be compensated for by changing the angle of the .ta ier bar 16.

he construction shown in Figs. 1 to 4 is preferable when relatively longblanks are to be cut. The thread on the screw 22 is of a finer pitchthan that on the lead screw 5 andv the result is that the slide 19 hasa. relatively short movement. This construction permits the carria e 4to be moved through a considerable dlstance without necessitating a longslide 19 and a long support therefor. hen shorter blanks are to bethreaded, the construction shown in Figs. 5 and 6 can be used.

What I claim is:

1. lhe combination of devices for holding a rotatable blank and athreading tool in operative engagement, mechanism including a rotatablelead screw for moving the tool longitudinally, a rotatable sleeve engag'the lead screw and fixed against lon 'tudinal movement with respectthereto, a xed element having threaded engagement with the sleeve, gearteeth on the sleeve, a transversely movable rack engaging ,the gearteeth, and angularly adjustable longitudinally movable taper bar formoving the rack, and means for moving the bar in timed relation with therotation of the lead screw.

2. The combination of devices for hold ing a rotatable blank and athreading tool in operative engagement, mechanism including a rotatablelead screw for moving the tool longitudinally, a rotatable sleeveengaging the lead screw and fixed against longitudinal movement withrespect thereto, a fixed element having threaded engagement with thesleeve, means includin a taper bar for rotating the sleeve, an meansincluding a rotatable screw operatively connected with the lead screwfor moving the bar lon tudinally in timed relation with the rotation ofthe lead screw.

8. The combination of devices for holding a rotatable blank and athreading tool in operative engagement, mechanism including a rotatablelead screw for moving the tool longitudinally, a rotatable sleeveengaging the lead screw and fixed against lon itudinal movement withrespect thereto, a xed element having threaded engagement with thesleeve, means including a taper bar for rotating the sleeve, and meansfor moving the bar longitudinally in timed relation with the rotation ofthe lead screw but at a. rate slower than that of the tool.

4:. The combination of devices for holding a rotatable blank and athreading tool in operative engagement, mechanism including a rotatablelead screw for moving the tool longitudinally, a rotatable sleeveengaging the lead screw and fixed against longitudinal movement withrespect thereto, a fixed element having threaded engagement with thesleeve, means including a taper bar for rotating the sleeve, and meansincluding a rotatable screw operatively connected with the lead screwfor moving the bar longitudinally in timed relation with the rotation ofthe lead screw but at a rate slower than that of the tool.

5. An attachment for a threading lathe or similar machine, comprising incombination a rotatable sleeve engaging the lead screw and fixed againstlongitudinal movement with respect thereto, a fixed element havingthreaded engagement with the sleeve, means including a taper bar forrotating the sleeve, and means including a rotatable screw adapted to beoperatively connected with the lead screw for moving the barlongitudinally in timed relation with the rotation of the lead screw.

In testimony whereof, I hereto aflix my signature.

FRIEDERIOH MULLER.

